A positive side gate power supply voltage VGH and a negative side gate power supply voltage VGL which are supplied to a driver IC (Integrated Circuit) for driving a display apparatus are generated by a voltage boosting circuit based on a reference power supply voltage VCI. FIG. 1 is a block diagram showing a part of the configuration of a conventional driver IC. The driver IC shown in FIG. 1 contains a voltage boosting circuit 101 which generates the positive side gate power supply voltage VGH based on the reference power supply voltage VCI1, and a VCI power supply 102 which generates a positive side reference power supply voltage VCI1. The voltage boosting circuit 101 and the VCI power supply 102 are both started up in response to a control signal SEQ_ON. Specifically, as shown in FIG. 2, the generation (voltage boosting) of the reference power supply voltage VCI1 and the voltage boosting of the positive side gate power supply voltage VGH are started in synchronization with an active edge of a control signal SEQ_ON.
For example, as shown in FIG. 3, the voltage boosting circuit 101 is provided with a charge pump circuit which has voltage boosting switches SW11 to SW14 and capacitances C1 and C2. Each of the voltage boosting switches SW11 to SW14 is exemplified by a transfer gate as shown in FIG. 4. In detail, each of the voltage boosting switches SW11 to SW14 is provided with a P-channel transistor MP1 having a source connected with a node N1 and an N-channel transistor MN1 having a drain connected with a node N2. The transfer gate controls an electric connection between the node N1 and the node N2 according to a clock signal CLK supplied to the gate of the P-channel transistor MP1 and a clock signal CLKB supplied to the gate of the N-channel transistor MN1.
The charge pump circuit shown in FIG. 3 outputs a voltage of twice of the reference power supply voltage VCI1, which is supplied to a node N11, as the positive side gate power supply voltage VGH by the charging and discharging the capacitances C1 and C2 through a switching operation by the voltage boosting switches SW11 to SW14.
The positive side gate power supply voltage VGH is supplied to a gate driving circuit (not shown) and is used as the positive side power supply voltage to drive gate lines of the display panel.